9,232 research outputs found
Economic evaluation of the treatment of grade II haemorrhoids : a comparison of stapled haemorrhoidopexy and rubber band ligation.
The definitive version is available at www3.interscience.wiley.comPeer reviewedPostprin
Discrete Lie Advection of Differential Forms
In this paper, we present a numerical technique for performing Lie advection
of arbitrary differential forms. Leveraging advances in high-resolution finite
volume methods for scalar hyperbolic conservation laws, we first discretize the
interior product (also called contraction) through integrals over Eulerian
approximations of extrusions. This, along with Cartan's homotopy formula and a
discrete exterior derivative, can then be used to derive a discrete Lie
derivative. The usefulness of this operator is demonstrated through the
numerical advection of scalar fields and 1-forms on regular grids.Comment: Accepted version; to be published in J. FoC
Dynamic evolution of the source volumes of gradual and impulsive solar flare emissions
This study compares flare source volumes inferred from impulsive hard X-rays and microwaves with those derived from density sensitive soft X-ray line ratios in the O VII spectrum. The data for this study were obtained with the SMM Hard X-Ray Burst Spectrometer, Earth-based radio observatories, and the SOLEX-B spectrometer on the P78-1 satellite. Data were available for the flares of 1980 April 8, 1980 May 9, and 1981 February 26. The hard X-ray/microwave source volume is determined under the assumption that the same electron temperature or power law index characterizes both the source of hard X-rays and the source of microwaves. The O VII line ratios yield the density and volume of the 2 X 10 to the 6th K plasma. For all three flares, the O VII source volume is found to be smallest at the beginning of the flare, near the time when the impulsive hard X-ray/microwave volume reaches its first maximum. At this time, the O VII volume is three to four orders of magnitude smaller than that inferred from the hard X-ray/microwave analysis. Subsequently, the O VII source volume increases by one or two orders of magnitude then remains almost constant until the end of the flare when it apparently increases again
Opaline Microfossils in Some Michigan Soils
Author Institution: Department of Agronomy, University of Illinois, Urbana, Illinoi
The experiences of women with polycystic ovary syndrome on a very low-calorie diet
The research was funded by an educational grant from LighterLife. Broom was the Medical Director for LighterLife at the time of the research. Johnson is the Head of Nutrition and Research at LighterLife. The authors report no other conflicts of interest in this work.Peer reviewedPublisher PD
Phase diagram of the one-dimensional Holstein model of spinless fermions
The one-dimensional Holstein model of spinless fermions interacting with
dispersionless phonons is studied using a new variant of the density matrix
renormalisation group. By examining various low-energy excitations of finite
chains, the metal-insulator phase boundary is determined precisely and agrees
with the predictions of strong coupling theory in the anti-adiabatic regime and
is consistent with renormalisation group arguments in the adiabatic regime. The
Luttinger liquid parameters, determined by finite-size scaling, are consistent
with a Kosterlitz-Thouless transition.Comment: Minor changes. 4 pages, 4 figures. To appear in Physical Review
Letters 80 (1998) 560
Quantum Entanglement in the Two Impurity Kondo Model
In order to quantify quantum entanglement in two impurity Kondo systems, we
calculate the concurrence, negativity, and von Neumann entropy. The
entanglement of the two Kondo impurities is shown to be determined by two
competing many-body effects, the Kondo effect and the
Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction, . Due to the
spin-rotational invariance of the ground state, the concurrence and negativity
are uniquely determined by the spin-spin correlation between the impurities. It
is found that there exists a critical minimum value of the antiferromagnetic
correlation between the impurity spins which is necessary for entanglement of
the two impurity spins. The critical value is discussed in relation with the
unstable fixed point in the two impurity Kondo problem. Specifically, at the
fixed point there is no entanglement between the impurity spins. Entanglement
will only be created (and quantum information processing (QIP) be possible) if
the RKKY interaction exchange energy, , is at least several times larger
than the Kondo temperature, . Quantitative criteria for QIP are given in
terms of the impurity spin-spin correlation.Comment: 7 pages, 3 figures, 1 tabl
Fourth International Bemisia Workshop International Whitefly Genomics Workshop December 3–8, 2006, Duck Key, Florida, USA
Observations of the structure and evolution of solar flares with a soft X-ray telescope
Soft X ray flare events were observed with the S-056 X-ray telescope that was part of the ATM complement of instruments aboard SKYLAB. Analyses of these data are reported. The observations are summarized and a detailed discussion of the X-ray flare structures is presented. The data indicated that soft X-ray emitted by a flare come primarily from an intense well-defined core surrounded by a region of fainter, more diffuse emission. An analysis of flare evolution indicates evidence for preliminary heating and energy release prior to the main phase of the flare. Core features are found to be remarkably stable and retain their shape throughout a flare. Most changes in the overall configuration seem to be result of the appearance, disappearance or change in brightness of individual features, rather than the restructuring or reorientation of these features. Brief comparisons with several theories are presented
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